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WAEC Further Mathematics 2021 Question 18

Question 18

Differentiation

If 2y2 + 7 = 3y − xy, find dy/dx.

  1. A.−y/(4x + y − 3)
  2. B.y/(4x + y − 3)
  3. C.−y/(4y + x − 3)
  4. D.y/(4y + x − 3)
Show the answer and explanation

Answer: C (−y/(4y + x − 3))

Explanation

4y dy/dx = 3 dy/dx − x dy/dx − y, so dy/dx(4y + x − 3) = −y and dy/dx = −y/(4y + x − 3).